1. Technical Field
The present invention relates to image sensing devices and methods, and more particularly to a back-illuminated photosensitive device having optical components wafer bonded to a passivation layer.
2. Description of the Related Art
Complementary metal oxide semiconductor (CMOS) image sensors are widely used for making high density or high resolution arrays of photodetectors. These image sensors are, in principle, classified into two categories depending on the direction that the incident light hits the sensor. These include a front-illuminated sensor and a back-illuminated sensor. It is commonly known that the back-illuminated architecture permits the implementation of a photodetector array with higher density and improved performance compared to the front-illuminated architecture. Reflectance of incident light from a metal interconnect surface limits the performance of the front-illuminated architecture due to cross-talk amongst individual cells and attenuation of the incident light intensity. Moreover, the presence of several levels of metal interconnect further tends to restrict the areal density of the image sensor array. As a result, the back-illuminated architecture is preferred to alleviate the shortcomings of the front-illuminated image sensor structure.